NEW YORK — Sulaiman Abu Ghaith, a son-in-law of Osama bin Laden who once served as a spokesman for Al Qaeda, pleaded not guilty at his arraignment Friday morning in US District Court in Manhattan, where he was charged with conspiring to kill Americans.
John P. Cronan, an assistant US attorney, said in court Abu Ghaith had spoken at length with US law enforcement officials after his arrest by federal authorities on Feb. 28. Cronan cited a 22-page document detailing his statements but did not characterize them. The statements were not made public.
The appearance of Abu Ghaith before Judge Lewis A. Kaplan in the cavernous, wood-paneled ceremonial courtroom in Lower Manhattan, just blocks from the site of the Sept. 11 attack, was not without symbolism. But details of both the defendant’s role in Al Qaeda and his arrest remained unclear.
Slight, trim, and balding with a manicured gray beard, Abu Ghaith was led into the courtroom wearing handcuffs and a blue prison smock as about a dozen US marshals — an unusually large complement — provided security. His handcuffs were removed for the proceeding.
Abu Ghaith said little beyond a few one-word replies to questions from the judge.
Philip L. Weinstein, one of three lawyers the judge appointed to represent him, entered a not guilty plea on his behalf during the proceeding, which lasted less than 20 minutes.
Cronan asked that Abu Ghaith be held without bail. Weinstein did not challenge the request but left open the possibility of making a bail application later.
Cronan said the government would take three weeks to present its case at trial, but no date was set.
Kaplan summarized the single charge facing Abu Ghaith and explained his rights. The proceedings were translated into Arabic for Abu Ghaith, who listened on headphones.
Justice Department officials described him as a propagandist. They said they believed that he had not had an operational role in Al Qaeda for years and that he did not participate in the attacks on Sept. 11, 2001. But one law enforcement official said that Abu Ghaith, 47, was the most senior Al Qaeda figure to face criminal trial in New York. He was married to bin Laden’s daughter Fatima, and the indictment alleges a working relationship with bin Laden, who was killed by US forces in 2011.
“Among other things, Abu Ghaith urged others to swear allegiance to bin Laden, spoke on behalf of and in support of Al Qaeda’s mission, and warned that attacks similar to those of Sept. 11, 2001, would continue,’’ the indictment said.
The decision to hold Abu Ghaith’s trial in the United States was criticized by some lawmakers. Senator Mitch McConnell of Kentucky, the Senate minority leader, said in a statement that Abu Ghaith had knowledge of Al Qaeda’s activities and that he should have been held at Guantanamo Bay, where he might have been ‘‘fulsomely and continuously interrogated without having to overcome the objections of his civilian lawyers.’’
Outside the courthouse, where dozens of news organizations stood vigil in the blustering wind and snow, there was a noticeable increase in security, with police officers patrolling the perimeter with bomb-sniffing dogs and extra barriers set up for crowd control.
Mayor Michael R. Bloomberg, speaking on his weekly radio program Friday morning, said he would not second-guess the decision to hold the trial in New York.
“No street is going to be closed because of this,’’ he said. ‘‘Would I prefer to have it elsewhere? I’m not going to get involved in that because I don’t want to make the president’s job any more difficult.’’
On the morning after the attacks, Abu Ghaith appeared with bin Laden and Ayman al-Zawahiri, then bin Laden’s deputy and now his successor. Abu Ghaith later delivered a speech warning that ‘‘the storms shall not stop, especially the airplanes storm,’’ and advised Muslims, children and opponents of the United States ‘‘not to board any aircraft and not to live in high-rises.’’
One person with knowledge of the circumstances surrounding Abu Ghaith’s arrest and his statements to FBI agents and New York police detectives from the Joint Terrorist Task Force said the suspect was disappointed but not surprised when he was arrested.
When Abu Ghaith spoke at length with investigators, before and after requesting a lawyer, he was consistently pleasant and respectful, the person said.
The person would not characterize the statements’ nature or value but said that whenever agents and detectives had a chance to talk to someone like Abu Ghaith, it was useful.
Cronan said during the hearing that Abu Ghaith had been taken into custody by US law enforcement officials about midnight Eastern time on Feb. 28 and arrived in New York about 12:30 p.m. the next day.
Other officials have said Abu Ghaith, who is said to have lived in Iran for the past decade, was initially detained in Turkey, while staying in a hotel in Ankara, but was taken into US custody in Jordan.